Drill-and-blast process

ABSTRACT

Working, e.g., excavating, a geological mass by a succession of substantially continuous drill-load-blast sequences, each sequence comprising drilling a hole in the mass, placing a charge of condensed secondary explosive in the hole, and initiating the charge by projecting propagative energy, e.g., the kinetic energy of a high-velocity projectile, through an inactive medium, e.g., the atmosphere, to the charge from a location which confronts, and is separated from, the hole in a manner such that energy is released into the charge at a rate sufficiently high to cause detonation thereof. An apparatus including drilling means, explosives-delivery means, and means for projecting energy, e.g., a gun, mounted on support means that preferably can be moved so as to position the drilling means, explosives delivery means, and energy-projection path sequentially on substantially a common axis.

[4 1 Apr. 15, 1975 United States Patet Bergmann et al.

tary Explosives, pp. 47-49 relied on, April, 1955 UFS- 23A51 1955 C4.

[ DRILL-AND-BLAST PROCESS [75] Inventors: Oswald R. Bergmann, CherryHill Township, N.J.; David L. Coursen, Newark Primary E.raminerVerlin R.Pendegrass d n d D a 0 mm. .m e im t n 0 P m U a w Lm .0 EC a e n. g n SA l 3 7 ABSTRACT 22 Filed: Dec.7, 1973 Appl' 422656 Working, e.g.,excavating, a geological mass by a succession of substantiallycontinuous drill-load-blast sequences, each sequence comprising drillinga hole in the mass, placing a charge of condensed secondary explosive inthe hole, and initiating the charge by projecting propagative energy,e.g., the kinetic energy of a high-velocity projectile, through aninactive medium, e.g., the atmosphere, to the charge from a locationwhich confronts, and is separated from, the hole in a manner such thatenergy is released into the charge at a rate sufficiently high to causedetonation 34 3 w [0M1 9 1 n 9 x0 1 .9 2 OC 2 l o y u m N 0 m a q 0 6 MUm 0 m mR 0 8 m In .m s n n m9 m. Q m m m PN mmm A. mu m ma 55 W2 Uf Th0 NC 0 r e n .a t. O huu S 8 m L R mo G nm M ma SL8 b i Ca UIF 11 1]] 3218 6 555 [[l.

[56] References Cited UNITED STATES PATENTS thereof. An apparatusincluding drilling means, explosives-delivery means, and means forprojecting energy,

XX 2 mm my Davis et al. Lewis et OTHER PUBLICATIONS Dept. of ArmyTechnical Manual, TM9-l9l0, Mili- ML raw mCr. nt S n b a ww m a JLA435008 56666 99999 111.11 8947 1 4 87 58523 .5 5 547200 80790 23333 9Claims, 10 Drawing Figures PATENTEB 5W5 3,877. 378

sumlp ig INVENTORS Oswald R. Berg monn BY David L. Cou r sen PATENTEUAPR1 EMS SHEET 2 BF 3 INVENTORS Oswqld R. Bergmunn BY DOVld L. C ou rs enPMEHTEBAPR 1 5 ms sum 3 9 3 INVENTORS Oswald R. Bergmunn David L.(Iqursen DRILL-AND-BLAST PROCESS This is a continuation, of applicationSer. No. 878,005 filed Nov. 19, 1969, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an improveddrill-and-blast process wherein a secondary explosive charge is loadedinto a drill hole and then initiated therein by the rapid release ofenergy projected to the charge through an inactive medium, e.g., theatmosphere, and to a drilland-blast module useful for carrying out theprocess in a rapid, cyclic manner.

Drill-and-blast processes have long provided man with a powerful toolfor performing useful work, affording the energy required, for example,for excavation operations of various kinds, i.e., operations in whichmaterial is dug out and removed at or below the earths surface either toform a useful cavity, e.g., in tunneling, or to derive profit from theremoved material, e.g., in mining. The explosive energy afforded bydrill-and-blast processes also has been utilized for other purposes,e.g., in seismic prospecting to provide information regarding thelocation of useful geological strata, such as gasor oil-bearing strata.At the present time there is an ever-increasing need for prospecting andexcavation operations, and especially for underground excavations, e.g.,for constructing water and vehicle tunnels, parking spaces, and militarydefense sites, and for exploiting very large mineral deposits underconservation constraints. However, significant reductions in cost andincreases in the sustained rate of working, e.g., tunnel advance, areneeded if prospecting and excavation are to be utilized effectively tomeet the challenges of urbanization and natural resource conservation.

In the conventional drill-andblast method of working a geological masssuch as rock for excavation thereof, holes are drilled in apredetermined pattern in the rock; after all of the holes have beendrilled, a secondary explosive charge is loaded therein, usually byhand; an initiating device, i.e., a blasting cap or primer, is placed incontact with the charge in each hole, or with detonating cord leading tothe charge, and connected to a remotely located common actuating devicesuch as a blasting machine; and the charges thereafter are initiated byenergizing of the actuating device. In underground excavation, after aventilation period or smoke time, which is necessary to clear theairborn fumes and dust produced as a result of such a blast, the roundis concluded with the mucking operation, i.e., the loading andtransporting of the disintegrated material (muck) from the excavation toa disposal area. This cycle is then repeated.

In recent years, mechanical excavators, or moles," have been developedwhich are capable of boring a tunnel or shaft, or mining out ore, bymeans of a rotating cutterhead driven by electric or hydraulic motors,the muck being picked up by a wheel which discharges it onto a beltconveyor that carries it back behind the machine. At their presentrespective levels of technological development, mechanical excavatorshave a greater driving capability per day in weak and mediumstrengthrock than the drill-and-blast method. This is due chiefly to the factthat the mechanical method involves a near-continuous operation,although delays are encountered because of changes in geologicalconditions, mechanical and electrical failures, the need for frequentcutter changes, etc.

There are serious limitations to the use of mechanical excavators,however. One of these is that mechanical excavators cannot be usedeffectively in hard and/or abrasive rock, e.g., rock having acompressive strength of more than about 15,000 psi or a Mohs Scalehardness greater than about 5. Rock of this nature is presentlyencountered in about one-third of the excavation projects, and it isexpected that this percentage will increase as future publicconstruction demands force excavations to be made at greater depths andin areas of known hard-rock conditions. A second limitation is that theinitial investment in mechanical excavators is high, and consequentlytheir use in many short tunnels cannot be economically justified eventhough the excavator would be technically capable of driving the tunnel.Furthermore, investment in a new excavator usually is necessary in eachmechanical tunnel-driving project because the different diameterrequirements and geological conditions encountered from project toproject necessitate the designing of a machine for each individualtunnel, even though machines which have been used in completed projectsmay still have some useful life. With respect to mining operations,continuous mining machines sometimes are too large and inflexible topermit the efficient mining of narrow ore seams. For reasons such asthese, the drill-and-blast method of excavation is the method of choicein many operations at the present time.

As now practiced, however, the drill-and-blast method of excavation hasinherent delays in each cycle which cause the rate of heading advance,or driving capablity per day, to be low. The low rate of advance,requirement of large labor crews, and costs of expended materials makethe total excavation costs high. Cycle delays and high manpowerrequirements are inherent in the procedures presently employed toprepare the formation for the disintegration step, i.e., the blast, andby the condition of the environment in the work area during and afterblast. The preparative operations include moving the drilling equipmentup to the face, drilling the holes, moving back the drilling equipment,charging the holes with secondary explosive, placing assemblies (i.e.,blasting caps) containing primary explosive charges in contact with thesecondary explosive, or in contact with detonating cords leading to thesecondary explosives in the holes, and connecting the assemblies thatcontain primary explosive charges to a source of energy so that acontinuous energy-storing, as well as energy-transmitting, circuit isformed from a remotely located common energy source, e.g., a blastingmachine or power line, to the secondary explosive charges. The initialenergy, e.g., an electrical pulse emitted by the common energy source,thus is transmitted to the secondary explosive through an active medium,i.e., one containing stored energy (the primary explosive), which isused in turn to initiate the secondary explosive.

Because of the time required to drill, load, and otherwise prepare theholes for blasting, it has been necessary, in the interest ofefficiency, to design the rounds (the drill hole arrangement at theface) to pull large cross-sectional areas of the face in one blast,e.g., the full cross-sectional area (full-face method), or a large partof it (top heading and bench method). Rounds of this size require alarge number of drill holes and consequently the detonation of a largenumber of explosive charges. For example, for a full-face round in atypical railroad tunnel 28 feet high and 21 feet wide, about 900 poundsof explosive may be detonated per round. Because of the pressure androck-throw effects resulting from blasts of this magnitude, theimmediate blast area must be cleared of personnel and equipment. This isthe reason why remote emission of the initiation pulse, and thereforeconnection of all of the charges into an energy-transmitting circuit,have been necessary.

Large single blasts such as have been employed here tofore can producestrong ground vibrations which may be detrimental to surroundingstructures. In addition, such blasts produce large quantities of airbomfumes and dust which must be exhausted before personnel can move in withmucking equipment. Usually fans must be operated for a period of atleast about twenty minutes to clear the area so that work can beresumed. After the smoke time," the mucking machine is moved in, theround is mucked out, and the mucker is moved out.

Drilling procedures have been made more efficient in recent years withthe introduction of modern drilling machines, such as pneumaticpercussive drills mounted on a drill jumbo (a mobile work platform), anddrill hole loading time has been reduced considerably with theavailability of such devices as a pneumatic cartridge loader havng asemiautomatic breech-piece for feeding cartridges into a loading tubecontinuously, and a robot loader for moving the tube in the drill hole.However, the efficient use of equipment and manpower still hasnecessitated large-round blasts, and delays therefore have remainedconsiderable owing to the time required for moving the drillingequipment up to the face to be blasted; moving it back before the blast;moving the loading personnel and equipment in and out; performing themanual operations of connecting the blasting leads (cap leg wires, orlengths of detonating fuse or safety fuse) to form a blasting circuit tothe remote actuating device; and smoke time.

The use of blasting caps in a remotely actuated large blasting circuitto initiate the charges in the drill holes in drill-and-blast processesthus can be seen to be uneconomical from the viewpoint of expenditure oftime and manpower. In addition, since the caps are consumed in theblast, their cost also is a factor to be considered. Also, with respectto safety considerations, the use of blasting caps is not entirelywithout risk since they contain a primary (highly sensitive) explosivecharge adjacent to a less-sensitive secondary explosive base charge,thereby forming a continuous reaction train from the primary explosivein the cap to the secondary explosive charge in the drill hole when thecap has been placed in initiating position. Thus it is most important toguard against accidental ignition of the ignition charge, adjacent tothe primary explosive charge, in the positioned cap as well as in capslocated in a storage area or in transit to the charge in the drill hole.Also, because of the interdependency of all of the charges in a roundwith respect to electrical initiation, once they have been connected,accidental generation of voltage at any one location in the electriccircuit is likely to set off all of the charges. Apart fromconsiderations of safety and materials cost, however, another seriousdrawback to the initiation methods now employed in blasting is that theyare not amenable to mechanization and efficient operation in small blastcycles and, consequently, represent a formidable barrier to theperformance of drill-and-blast operations on a rapid, near-continuousbasis, i.e., in a substantially continuous cyclic succession ofuninterrupted drill-loadblast sequences, a manner of operation whichobviously is the most reasonable approach to decreasing cost and time.Such mechanization and small-blastcycle operation not only would greatlyincrease the efficiency of drill-and-blast excavation operations, butalso would provide an efficient means of utilizing the drill-and-blasttechnique for the common-depth-point method of seismic prospecting.Particularly in areas where the surface layer (e.g., fractured rock,coral, unconsolidated ice or frozen ground) strongly absorbs seismicenergy, the use of explosives in drill holes in the latter method wouldprovide higher-energy signals and information concerning deeper layersthan the gas exploders currently in use.

SUMMARY OF THE INVENTION This invention provides an improveddrill-and-blast process in which secondary explosive charges confined indrill holes in a geological mass to be worked, e.g., rock, are initiatedby the rapid release therein of energy projected to the charges in thedrili holes through an inactive medium, e.g., the atmosphere, ratherthan via a continuous reaction train containing a primary explosive.More specifically, the process of this invention comprises performing asuccession of substantially continuous drill-load-blast sequences, eachsequence at a single location in the mass different from the locationswhere other sequences are performed, and each sequence comprising thesteps of (a) drilling a hole in the mass; (b) placing a charge ofcondensed secondary explosive in the hole so that the explosive isconfined and supported by the wall of the hole; and (c) initiating theexplosive charge in the hole by projecting propagative energy, e.g., thekinetic energy of a high-velocity projectile, through an inactivemedium, e.g., the atmosphere, to the charge from a location whichconfronts, and is separated from, the hole in a manner such that energyis released into the charge at a rate sufficiently high to causedetonation thereof. Preferably, and especially when the process is anexcavation process, the succession of sequences is also substantiallycontinuous, i.e., the process is comprised of substantially continuousdrill-load-blast sequences in substantially continuous succession.

Propagative energy is energy which derives from the intensity and timedependence of the dynamic physical phenomena utilized to transport itfrom one place to another, e.g., the energy which derives from theintensity and time dependence of an electromagnetic field or of shockwave pressure, the velocity of a projectile, etc.

The term inactive medium, as used herein to describe the environmentthrough which the propagative energy is projected to the charge, denotesa medium, e.g., the atmosphere, which contains no stored energy of itsown, thus making no energy contribution to the initiation process. Thus,the energy is projected into the charge in the absence, or without theintervention, of a primary explosive in a physically continuous reactiontrain with the charge, or, more specifically, in the absence of ablasting cap.

A sequence as used herein denotes a drill-load (charge placement)-blast(charge initiation) operation at a given location (drilling a hole,loading the same hole with explosive, and initiating the explosive inthe same hole). The sequence is followed by one or more other suchsequences at different locations, thereby producing a succession ofsequences or cycles.

The term substantially continuous," when used herein to describe thedrill-load-blast sequences, means that the steps of the sequence followclosely one upon the other without the intervention of additional stepswhich are not directly concerned with operations performed on the massbeing worked. For example, the sequences are not interrupted for thelength of time required to move vehicular equipment back away from theformation and move different equipment up, connect blasting leads to theexplosive charges, and move all equipment and personnel out of the areato a remote position. A substantially continuous sequence in the presentprocess typically is one in which the total dead time, i.e., the timebetween drilling and charge placement steps plus the time between chargeplacement and charge initiation steps, is only on the order of fiveminutes or less.

The term substantially continuous when used herein to describe thesuccession of sequences in a preferred embodiment, has generally thesame connotation as described above for continuity of sequence steps.That is, sequence follows closely upon sequence, either before or aftercompletion of the previous sequence, from the first to the last in thesuccession, without delays or interruptions between the last step of onesequence (blast) and the first step of the next (drill) to exhaust thearea of fumes or move equipment up to the mass from a remote position. Asubstantially continuous succession of sequences in the present processtypically is one in which the dead time, i.e., time between sequences,is less than about minutes, dead time between sequences in the presentprocess, when used for excavating, usually being much less, i.e., lessthan about 1-2 minutes.

In a most efficient embodiment of the process, a number of sequences arecarried out substantially concurrently as a group or set of sequences,followed by one or more other such groups in, usually substantiallycontinuous, succession. in this case, each cycle of the cyclic processor succession is a cycle of groups of sequences. The term substantiallyconcurrently as applied herein to the performance of the sequences in agroup denotes that all of the sequences are begun and completed over aselected time period after which an other cycle begins. The term is notused to imply that the same step is carried out in every sequence of thegroup at precisely the same time.

All drill-load-blast sequences, and preferably also cyclic successionsof sequences or groups of sequences, are carried out substantiallycontinuously, as explained above. However, the specific time employedper sequence and succession, and the time pattern in which the sequencesare performed relative to other sequences can vary depending on suchfactors as the equipment available, working space available, etc. One ormore drills, one or more explosive loaders, and one or moreenergy-projecting devices can be employed.

For carrying out the process more rapidly and efficiently, especially inconstricted areas, a novel drilland-blast module also is provided by thepresent invention, the module comprising, in combination,

a. drilling means comprising an elongated member,

e.g., a drill steel, having a bit at one end, and positioned on supportmeans in axially movable relationship therewith;

b. explosives-delivery means for delivering explosive into a hole madeby the drilling means, the explosives-delivery means being positioned onsupport means in axially movable relationship therewith and inpredetermined alignment with respect to the drilling means, theexplosives-delivery means comprising a tube having one discharge end andan explosives feed end; and

means for projecting energy, e.g., a gun, for initiating explosivedelivered into a hole by the explosives-delivery means, theenergy-projecting means being positioned on support means inpredetermined alignment with the drilling means and explosives-deliverymeans; the drilling means, explosives-delivery means, andenergy-projecting means being (1) supported in a manner such that thebit of the drilling means, discharge end of the explosives-deliverymeans, and energy-exiting end of the energy-projecting means, e.g., agun muzzle, are located near a common, operating end, and (2) positioned, or adapted to be positioned, in a manner such that theenergy-projecting means projects energy on a path that leads into anexplosive charge delivered by the explosives-delivery means into a holedrilled by the drilling means; the movable relationship of the drillingmeans and explosivesdelivery means with the support means being suchthat the bit of the drilling means and the discharge end of theexplosives-delivery means extend sequentially beyond all othercomponents of the module in an axial direction at the operating end.

The module, when positioned near a mass of material to be blasted, e.g.,a rock face or the earths surface, and suitably energized, in rapidsequence drills a hole in the material, loads explosive into the hole,and initiates the explosive by the projection and release of energy intothe explosive, preferably by projectile impact, and can repeat thesequence at any desired number of other locations. For this reason, thethree working components, i.e., the drilling means, explosivesdeliverymeans, and energy-projecting means, are positioned, or adapted to bepositioned, in a manner such that the explosives-delivery means deliversexplosive into a hole made by the drilling means, and theenergyprojecting means projects energy on a path that leads into theexplosive in the hole. in other words, the longitudinal axes of thedrilling means, explosives-delivery means, and. energy-projecting meanspass, simultaneously or sequentially, through substantially a commonpoint in space located a desired distance outside the module near theoperating end corresponding to the location at which the drill bitinitially penetrates the formation, i.e., at the mouth of the drillhole. By substantially a common point we mean that at the desiredlocation outside the module, i.e., at the mouth of the drill hole, on anormal to the drill axis the three longitudinal axes all pass throughthe same point, or the axes of the explosives-delivery means andenergy-projecting means pass through points which are within one drillhole radius from the point through which the drill passes (i.e., on theaxis of the drill hole). This passage through substantially a commonpoint may be accomplished by positioning the three working components onaxes which converge at the desired point, or by providing positioningmeans, e.g., and indexing mechanism, to cause the axes substantially tocoincide sequentially. The converging non-coincidable design, whilefeasible, is not preferred, however, since it requires a precisepositioning of the module with respect to distance from a point on themass to be worked and precise maintenance of the same distance throughthe entire drilling, loading, and initiation sequence. Therefore, in apreferred embodiment, the support means cooperate(s) with a positioningmeans adapted to sequentially position, e.g., by pivoting and/orsliding, the drilling means, explosives-delivery means, andenergyprojecting means on substantially a common longitudinal axis.

The longitudinal axes of the drilling means, explosives-delivery means,and energy-projecting means which sequentially coincide or converge asdescribed are the longitudinal axis of the elongated member, e.g., thedrill steel, to which the bit is attached, the longitudinal axis of thebore of the delivery tube, and the axis along which the energy isprojected from the energyprojecting member, e.g., the longitudinal axisof a gun bore.

The term module is used herein to denote an apparatus which is afunctional unit or assembly of components adapted to be operative as aunit within a larger assembly in which it can be interchanged withanother such unit and, if desired, operated together with other suchunits.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing, whichillustrates specific embodiments of the invention,

FIGS. ll through 4 are longitudinal cross-sectional views of a typicalmodule of this invention through a given, substantially vertical plane(with respect to the horizon) at different times;

FIGS. 1A through 4A. are cross-sectional views of the module shown inFIGS. 11 through 4, respectively, as observed through a given verticalplane substantially normal to the plane of view of FIGS. 3 through 4 andintersecting said plane at the location indicated by dotted line A-A'and viewed in the direction of the arrows;

FIG. 5 is a longitudinal cross-sectional view of a portion of a moduleof this invention in which the energyprojecting means differs from thatshown in FIGS. ll through 4; and

FIG. 6 is a front, partially plan, view of a face in a geological massbeing worked in small blast cycles according to the process of thisinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present process, chargesof condensed secondary explosive are confined in drill holes andthereafter are initiated, each by rapidly releasing energy into thecharge by projecting propagative energy to the charge through aninactive medium, e.g., the atmosphere..This mode of initiation isdifferentiable from those which employ a primary explosive in acontinuous reaction train with the charge, and from that which isemployed in drill-and-blast processes as commonly practiced, i.e., theinitiation of the charges in all of the drill holes by a common energyemission i.e., an electrical pulse or flame, generated remote from thedrill holes, the multiple charges having previously been joined togetherin a single energy-transmitting circuit. Use of the method of initiationemployed in the present process eliminates the time-consuming operationsrequired to prepare conventional electrical or non-electrical blastingcircuits, reduces manpower requirements, and permits excavationprocesses to be effected with considerably smaller blast cycles thanheretofore. In addition, the hazards of accidental detonation which areencountered when sensitive primary explosive compositions, as inblasting caps, are present in continuous reaction trains with thecharges are avoided.

An efficient drill-and-blast process requires that as much as possibleof the available explosive energy be manifest in the form of highpressure working on the formation surrounding the drill hole, e.g., tobreak the formation. This is accomplished by having as much of theexplosive as possible surrounded by the formation with avoidance of anysubstantial intervening compressible layer, e.g., an air annulus,between the explosive and the formation. For this reason, the explosivecharge is positioned within a drill hole so that it is confined by theformation and contacts the walls of the hole sufficiently to besupported thereby. In each drillload-blast sequence, the hole is drilledat the selected location, and then the explosive is loaded into thedrilled hole, by any of the various ways that are suitable for the typeof explosive charge employed, and the length and direction of the hole.For example, if the charge consists of one or more explosive cartridgesor packages, or a solid explosive in bulk, pneumatic loading may beemployed. Water gel explosives can be pumped in. The velocity of loadingshould be low enough that the explosive does not detonate spontaneouslyby impact with the formation or with a previously loaded cartridge. Suchspontaneous detonation during loading is avoided since it can destroythe loading equipment.

The selection of the explosive to be used in the present process ismade, as in any blasting process, on the basis of safety, performance,convenience, and economics. To provide the pressures required in hardrock, the explosive should be a condensed, e.g., solid (cast or packedpowder), semisolid, or liquid, detonating explosive, and it should berelatively insensitive to heat and mild shock, i.e., it is a secondaryexplosive rather than a primary explosive. A primary explosive is onewhich detonates when brought in contact with a flame or incandescentwire, whereas secondary explosives require, at least in practicalcommercial application, the use of a detonator and frequently a boosterfor initiation of detonation (Melvin A. Cook, The Science of HighExplosives, Reinhold, 1958, pp. 1-4). Representative secondaryexplosives include dynamites, ammonium nitrate/fuel oil mixtures, TNT,PETN, nitrostarch, and the currently popular water-bearing explosives asexemplified in US. Pat. Nos. 3,202,556, 3,355,336, 3,431,155 and3,444,014. The ingredients of the explosive composition can be pre-mixedand the mixture loaded into the holes, or, where feasible, as in thecase of ammonium nitrate prills and fuel oils, the ingredients can bemixed during loading by feeding into a common stream, or loadedseparately and mixed in the holes. The explosive charge in a given drillhole can be uniform in composition and/or density throughout its length;or different compositions, or the same composition at differentdensities, can be employed. If a particular selected composition isinsufficiently sensitive to a given energy-projecting system, successfuldetonation can be achieved by adding a small amount of a sensitizingingredient, e.g., a finely divided metal fuel, to the composition, ormaking the charge more sensitive only in the portion thereof where theenergy is initially released, e.g., the portion where projectile impactoccurs, care being taken, however, to avoid sensitizing the charge tothe levels characteristic of the primary explosives (e.g., leadstyphnate or lead azide), which are unsafe to handle in bulk under fieldconditions. Special sensitizing measures may be avoided, however, byaltering conditions in the energy-projecting system, such as projectilevelocity, area of impact, nose configuration, etc., as will be describedhereinafter.

After the drill holes has been loaded, the charge of secondary explosivetherein is initiated by means of propagative energy projected to thecharge through an inactive medium from a location which confronts, andis separated from, the hole, the energy being released into the chargeat a high rate per unit volume of charge in the vicinity of energyrelease. High rate of release is required to achieve a high localpressure and thereby to initiate detonation. Various types ofpropagative energy can be so projected and released to produce therequired detonation. For example, kinetic energy of motion (e.g., via aprojectile), electromagnetic radiation (e.g., via a focussed pulse oflight from a laser), or electrical energy (e.g., via a high-energyelectrical discharge through an electrode) can be used. The mediumthrough which the energy travels to the charge from the point ofprojectionor emission, e.g., a gun chamber, a laser, or a source ofelectrical energy such as a capacitor, is inactive (i.e., contains nostored energy), and in most instances will simply be the atmosphere inthe vicinity of the mass being worked. In the case of electrical energy,the energy is transmitted at least in part through an electrode. Sincethe energy is projected locally and a pulse of energy is projected foreach of the charges, the initiation step can be performed after loadingwithout the delays required to connect the charges to each other and toa common energy source. This permits efficient blasting in small blastcycles.

Of the various ways of projecting and releasing energy that can be usedin the present process, propulsion of a high-velocity projectile andimpact thereof with the charge are preferred from the standpoint of easeof operation and availability and cost of equipment. Vari ous kinds ofprojectiles and ways of propelling the projectile can be employed,provided the impact velocity is sufficiently high and the mass of theprojectile sufficiently great to release the energy at a sufficientlyhigh rate, i.e., to subject the charge to high enough pressure over asufficient area and time that it is caused to detonate completely at itsexpected velocity under the conditions prevailing in the drill hole.Complete, highorder detonation is required so that the maximum potentialof the explosive, e.g., for fragmenting, or introducing seismic energyinto, the surrounding formation may be utilized. Thus, as used herein,the term initiation refers to the supplying of an impluse which bringsthe explosive charge in the drill hole to complete detonation at a ratewhich falls within a range commonly encountered with the particularexplosive composition in question when initiated by conventional means.Generally, propagative energy is projected from a location which is lessthan about thirty feet from the portion of the mass being worked.

In the preferred case of projectile impact initiation, the chief factorsdetermining whether or not such detonation will occur in a givenexplosive are the velocity of the projectile on impact, the shockimpedance of the projectile, and its mass and shape. The minimumprojectile velocity is higher as the sensitivity of the explosive toimpact and the shock impedance of the projectile are less. For a givenexplosive and projectile material, the minimum impact velocity requiredto produce detonation usually is lower as the mass of the projectile isgreater (up to a certain maximum) and the area of the projectile nose,i.e., the area of the projectile surface which impacts squarely againstthe explosive, is larger. Also, for a given system and with a blunt-noseprojectile, the required detonation may be achieved at lower impactvelocities if the trajectory of the projectile is substantially on thedrill hole axis (head-on or non-glancing impact). As will be seen fromthe subsequent examples, certain dynamites are initiated reliably by0.22-caliber bullets (3.5 grams; pointed nose) at impact velocities aslow as 1,500 feet per second, while certain water-gel explosives requirehigher impact velocities, e.g., about 2,800 feet per second, with thesame ammunition. On the basis of wider applicability with respect toexplosives with which the projectile system is useful, therefore, asystem in which bullets are propelled to at least about 3,000 feet persecond muzzle velocity (about 2,800 feet per second impact velocity at adistance of 15 feet from the muzzle) is preferred.

The projectile is a body of material propelled to high velocity. It canbe a unitary solid, e.g., a bullet, or solid particles, e.g., shot. Ahigh-velocity fluid jet, such as a water jet, also can be used. Sincethe required impact velocity and high projectile shock impedance can beattained more readily with solid projectiles, solids are preferred, andparticularly unitary solids. Unitary solid projectiles should be made ofmaterials, preferably metals, which are strong enough to withstand thepressure and heat applied during propulsion. Their configuration isgenerally cylindrical with their forward end pointed or blunt, orspherical. For explosives which are initiated readily by projectileimpact, e.g., gelatin dynamites, the pointed-nose bullet found incommercial ammunition rounds can be employed. For less-sensitiveexplosives, it may be helpful to use a blunt-nose bullet, or one whichhas a conical cavity in the nose surface. Although the nose of theprojectile may carry a secondary explosive charge thereon to assist inthe initiation, inert projectiles are preferred since they are safer tostore and deliver, and cheaper. When the projectile is propelled, thegun can be in substantial axial alignment with the drill hole, orpositioned at a small angle thereto. Substantial axial alignment ispreferred to assure accuracy of impact and complete detonation. However,especially if the projectile has a pointed nose, the projectile can comein at an angle, e.g., up to about 15 to the hole axis, the allowablemisalignment in any given case depending on the nature of the mass beingworked and impact conditions.

The type of gun employed to propel the projectile is not criticalprovided it is capable of affording the required muzzle and impactvelocities with the type of projectile and propellant, or ammunition,used. Any small arms, e.g., rifles, shotguns, and pistols, can be used.Air guns also can be employed.

Another suitable way of initiating the explosive charge in the drillhole is to impinge the focussed output of a pulsed laser onto thecharge. In such an embodiment, the ease of initiation of a givenexplosive charge can be enhanced by increasing the power of the laser,e.g., by use of a Q-switched rather than a freerunning laser, and byhaving the end of the charge nearest the mouth of the drill hole undersuitable confinement. For example, a transparent plastic layer can beemployed over the end of the charge, either as a separate unit, or as anend of a cartridge unit, and the focussed laser beam allowed to passthrough the plastic to the charge. While the specific amount of energyrequired to initiate an explosive reliably by a laser beam varies withthe particular explosive composition, for the more sensitive secondaryexplosives such as pentaerythritol tetranitrate, gelatin dynamites, etc.about 0.025 joule/sq mm or more of incident energy is capable of causinginitiation when a Q-switched laser beam is focussed on the surface ofthe charge. Often the charge can be made more sensitive to initiation byincorporating in it a small amount of material having a highlight-absorption coefficient, e.g., carbon black. This increases therate of release of the energy per unit volume.

In still another method of initiating the explosive charge in the drillhole, one or more expendable electrodes are positioned in, or in closeproximity to, the charge, e.g., by means of a wire-feeding mechanism,such as those that have been developed for feeding welding wire off aroll, and energy is projected through and along the electrode byelectrically discharging a capacitor bank through the electrode.

A great advantage of the present process is derived from the fact thatall of the process steps, including initiation of the charges, areperformed locally, with the necessary equipment operating close to themass being worked on. Thus, the energy to be released into the chargesis projected from a location which confronts the mass, although beingseparated from it. The minimum distance between the energy-projectingdevice, e.g., a gun, and the drill holes will depend chiefly on thetotal weight of explosive detonated in one blast cycle (i.e., in holesdetonating within milliseconds of each other), the nature of the rockbreakage produced (direction and velocity of missiles), and theimpactand shock-resistance of the device. As a general rule, theenergy-projecting device will be separated from the mass by a distancewhich is approximately proportional to the cube root of the weight ofexplosive detonated per cycle. Although large separation distances canbe employed, e.g., up to about one to two tunnel or shaft diameters, itis preferred to work as close to the mass as is feasible with theequipment used. This is especially true when the drill-and-blast moduleof the invention is employed. In such a case, the module is positionedclose enough to the face for the drill to make the desired size hole,e.g., within a few feet, and it is more efficient to perform the blaststep, e.g., fire the gun, with the module in about the same position, orat any rate to avoid having to move the module back from the face beforeblasting.

The length of the explosive charge with respect to the length of thedrill hole will vary depending on the type of work being performed. Inexcavation, it normally will be more efficient to substantially fill thehole with explosive. A layer of gas or liquid, e.g., air or water, or

a solid layer, e.g., carboard or plastic, between the mouth of the drillhole and the end of the charge where the energy is to be released doesnot preclude satisfactory initiation of the charge under certaincircumstances, although the nature and maximum depth of such a layer,beyond which initiation becomes impossible or erratic, varies with theparticular type of propagative energy used for initiation, the explosivecomposition, and the magnitude of the energy. Any material between themouth of the drill hole and the end of the charge where energy is to bereleased, as well as between the energy-projection location and themouth of the drill hole, should be a material which, in the amountpresent, does not absorb a major fraction of projected energy. Forexample, a light-absorptive, light-scattering or light defocusingenvironment should be avoided between a laser device and the charge, andan electrically conductive environment should be avoided around anelectrode. With laser initiation, any optically transparent material canbe present. In the case of initiation by projectile impact, gases can bepresent, as well as liquids or solids to a certain depth. For example,explosives such as certain dynamites (GELEX 2), when wrapped in a papercartridge (cartridge end about three-eighths inch thick, for example)and covered by a layer of water up to about four inches thick in a1.75-2.00-inch-diameter drill hole, can be initiated reliably by theimpact of a commercial fully jacketed 0.22-caliber bullet (3.5 grams)impacting the water at a velocity of about 2,8003,600 feet per second.In practice, any layer of liquid or solid material present over the endof the charge usually will be due to conditions encountered in the areato be blasted, e.g., water, or to the condition -of the explosivecharged, e.g., a cartridge end.

The location pattern of the sequences (hole pattern), the time patternin which the drill-load-blast sequences are performed, the number ofsequences carried out concurrently (holes per cycle), and the amount ofexplosive detonated per sequence or concurrent group of sequences areall conditions that can vary widely, depending on many factors such asthe nature of the work to be performed, the overall size and physicalproperties of the mass being worked, the number of drill-andblastmodules (or separated components) available, the impactandshock-resistance of the equipment (since it confronts the mass duringblast), the degree of constriction of the working area, ventilation andnoise abatement requirements and capability, etc. For operations such asin seismic prospecting, secondary blasting, etc., one vehicle-mountedmodule may be moved along the surface as required and employed toperform a succession of single rapid drill-load-blast sequences atdesired locations in a desired time pattern. In operations such astrenching or underground excavation, the use of multiple modules toperform multiple sequences concurrently in groups is more efficient,more modules (or more sequences per group or cycle) giving fasteradvance. The specific number of sequences employed per concurrent group(i.e., holes per cycle) depends on the number of modules, and the space,available, the impactand shock-resistance of the modules, and mountingassembly employed, how close to the face the modules are employed, thesize of the charges, and the time interval between blasts. Consideringall of these factors, in most cases the size of the cycles will be lessthan about one-half the size of the entire round, most often up to about35% of the total number of holes required, or such that no more thanabout 100 pounds, usually up to about 30 pounds, of explosive detonatesper cycle.

The angle of the drill holes with respect to the face also will dependon the type of work desired. In some instances, the holes will need tobe drilled non-normal to a face because of space restrictions at thesides, roof, and floor of a tunnel. In other instances, oblique holeswill be used to provide a special type of cut. Any of the patternscommonly employed in drill-and-blast operations can be employed in thepresent process.

The present process can be used for excavating in any geological mass,but is particularly advantageous when used in hard abrasive rock, e.g.,rock having a compressive strength of more than about 15,000 psi or aMohs Scale hardness greater than about 5, where mechanical excavatorsare presently ineffective. Moreover, since the application of theprocess is applicable to a wide range of geological conditions, theprocess offers the important advantage of being adaptable to use withchanging conditions as are commonly encountered, i.e., major differencesin rock types and arrangements occurring within relatively smallvertical and horizontal distances. Naturally, the process can beemployed in excavating for construction purposes, as well as for mineralrecovery, e.g., ferrous and nonferrous metal ore mining, stone miningand quarrying, etc., and in seismic prospecting operations.

The drill-and-blast module of the present invention incorporates threebasic working components within its structure, i.e., drilling means,means for delivering explosive comprising an explosives-delivery ordrill-holeloading tube, and energy-projecting means, e.g., a gun, aswell as support means on which the three other components are mountedand which maintain(s) the required positions of the three componentsrelative to one another. Any mounting scheme which is convenient can beemployed provided the working end of each component, i.e., the drillbit, discharge end of the delivery tube, and energy-exiting end of theenergyprojecting member, e.g., the gun muzzle, are located near a commonend, i.e., the operating end of the module, and provided the componentsare capable of rnoving as required, i.e., the drill and delivery tubemovable axially with respect to the support means, and, in the preferredembodiment, a support means movable, e.g., pivotally and/or slidably, soas to permit the three basic components to be positioned sequentially ona corn mon axis. With these basic components and motions, the modulecan, in rapid sequence, drill a hole in a geological mass, loadexplosive into the drill hole, and initiate the explosive, and rapidlyrepeat the sequence, thereby performing the desired work on the mass.

The general configuration and dimensions of the module will bedetermined on the basis of economic factors as well as on the range ofdrill hole depths it will be required to produce and load, the numberand types of constructional elements and types of driving mechanismsemployed in the module, the positions of the basic components relativeto one another, etc. Considering the relative dimensions of drill holescommonly employed in blasting, i.e., diameters of about 0.5- inches anddepths of up to about 100 feet, and avoiding telescoping components,which, while feasible, are not preferred since their dependable repeatedfunctioning in a possibly dusty atmosphere may be difficult to achieve,the module usually will be elongate, i.e., long in proportion to itswidth. The overall configuration of the module, i.e., the shape of thebody formed when one or more surfaces are generated about the peripheryof its components, is immaterial to its operation, and can be generallycylindrical or prismoidal, with any convenient cross-section, e.g.,circular, oval, or polygonal, as is the case when the basic componentsare substantially parallel to one another; or frustoconical orwedge-shaped, as may occur when the axes of the basic components areconvergent. Since, as has been mentioned previously, it is preferredthat the proper positioning of the basic components during theiroperation depend on a sequential coinciding, rather than on aconvergence, of their axes, and since convergence is unnecessary whenthe axes are adapted to coincide sequentially, as well as less efficientwith respect to space utilization, substantially parallel positioning ofthe basic components, and therfore a generally cylindrical module, arepreferred. In this preferred embodiment, it will be understood that thecross-sectional area of the cylinder along the cylindrical axis mayvary, e.g., decrease from one end to the other, because of the presenceof certain constructional elements, or a slight obliqueness e.g., up toabout 10, of the basic component positions with respect to thecylindrical axis.

The support means for the three working components can be a unitaryelement, e.g., a rod, bar, pipe, or slab, or a skeletal framework ofelements, of rigid construction, preferably made of meta], e. g., steel.If an external housing member, such as a cylinder or box, is employed toprotect the components against impact, the housing member can serve as asupport means with each of the three components mounted in the housingwall. Alternatively, the housing member can serve as a support alongwith an internal support. For example, when the energy-projecting meansis a laser, it may be desirable to mount the laser in the wall of thehousing member, and the explosives delivery tube and drilling means on acommon internal support means. Any convenient means of mounting thecomponents onto the support can be employed, provided that the drillingmeans and explosives delivery tube are capable of unobstructed axialmotion with respect to the support so that they can both sequentiallyextend beyond all other components of the module at the operating end,the drill bit being capable of extending beyond the other components fora distance at least equal to the depth of the drill hole required, andthe delivery tube for only the short distance, at the minimum, requiredto insert its discharge end into the drilled hole, although preferablyit will be capable of extending farther into the hole.

ln order that the module perform in a predetermined manner, i.e., thatthe achieved conditions such as the location and angle of the drilledhole, explosive loading and density, and trajectory of the projectedenergy, are in accordance with the preselected conditions, it isnecessary that the relative positions of the basic components bemaintained during operation of the module, that is, that the componentsbe supported while in extended as well as retracted positions. For thisreason, it is preferred that any axially movable basic component whichis insufficiently rigid to maintain its required position duringoperation be held in position by the support for a major portion of thecomponent's length, and more preferably for essentially its full length,when in the retracted position, and that the distance between the end ofthe support at the operating end of the module and the mass to be workedwhen the component is extended beyond the support end, be insufficientto cause the component to move out of its predetermined axial position.Added assurance of good positioning of the extensible components isachieved by providing guide means on the support near its end throughwhich the components travel as they move axially beyond the support end.Also, the distance between the end of the support and the face can bedecreased without having to move the entire module closer to the face byhaving the support independently axially movable with respect to amodule mounting member to which it is affixed. A protruding peg capableof anchoring itself in a rock formation, e.g., by a piercing (a stinger)or suction action, can be provided at the end of the support means, ifdesired.

The specific distances to which the axially movable components can beextended are not critical to the function of the module and depend onthe depth of drill hole(s) required and how close to the face the moduleis operated. From a given operating position of the module, theexplosives delivery tube need not extend as far as the drill bit, andboth tube and drilling means will extend farther than the support whenthe latter moves with respect to a mounting member.

The module is adapted to be mounted on an external supporting arm,preferably via the support means in the module. While the module ssupport means may be designed to permit it to be joined directly to anexternal supporting arm, it usually will be more practical to affix aseparate mounting member to the modules support, this mounting memberlater to be joined with a mounting member on the external supportingarm. A convenient construction is one in which the modules mountingmember affords the re-positioning capability required of the basiccomponents to cause them to sequentially coincide. For example, themounting member may incorporate a pivot, permitting the support meanscommunicating therewith to rotate. Alternatively, the re-positioningalso may be accomplished by a lateral sliding of the support means.Pivoting and/or sliding of the support means and the locking of thesupport means in position is accomplished by energizing of an indexingmechanism communicating with the mounting member or support means. Theindexing mechanism can be, for example, an hydraulically actuatedmechanism, providing either linear motion, as does an hydrauliccylinder, or rotary motion, as does a rotary actuator. Preferably, theindexing mechanism communicates directly with the mounting member forthe module, e.g., a groove-containing member through which the supportmeans slides in an axial direction. With respect to pivoting motion, apreferred procedure is to have the drilling means on the desired axis inthe rest (vertical) position, with the explosives delivery tube andenergy-projecting means mounted on the same side, or opposite sides, ofthe drilling means and rotate the support in one direction to positionthe tube on the axis desired, and farther in the same direction, or inthe opposite direction, to position the energyprojecting path thereon.

All of the structural components of the module, as well as themotion-imparting mechanisms therein, must be shielded against theeffects of air blast and possible missile impact resulting from thedetonation of the explosive charges in the drill holes. Such shieldingmay be provided, for example, by a transverse metal plate (i.e., a platemounted with its large surfaces substantially normal to the module axis)between the module(s) and the mass being worked, with the module(s)operating through apertures in the plate. Such shielding for themodule(s) affords less maneuverability of the module, however, and isnot readily adaptable for use with masses of all sizes. Therefore, it ispreferred that the module components be surrounded by a shockandimpact-resistant shielding means, i.e., a housing member, permitting themodule to be operated in direct confrontation with the mass with noadditional shielding necessary between module and mass. The housingmember is made of a sufficiently tough material, e.g., a metal such ascertain steels, and is sufficiently thick that it will not rupture orplasticially deform to any great degree as a result of the shockpressures and missile (rock) impacts to which it is exposed. For a givenmetal, the minimum necessary thickness of the housing will be determinedin any given case by the size of the blast (i.e., amount of explosivedetonated), size and velocity of rock fragments produced, how close tothe blast the module operates, etc. For operation under moderateconditions, e.g., blasts of less than about 4 pounds of explosive, rocksup to about 12 inches in size and moving at velocities up to about 40feet per second, and distances of at least about 2 feet between themodule and face, a housing which has a shell at least about 0.5 inchthick may be employed. Like the configuration of the module, theconfiguration of the housing member is immaterial, but usually it willbe generally cylindrical or prismoidal, as described previously for themodule configuration.

Usually the module will be mounted in the housing member wall byaffixing to the housing wall a mounting member which is in engagementwith the support means of the module. Affixing the support meansdirectly to the housing wall is not preferred since repositioning of thecomponents would, in such a design, require movement of the housing aswell.

The housing member, like the module itself, is elongate, and, since itis required to shield all of the module components, at least during theblast, the operating end of the housing member is adapted to be closed.The non-operating end can be open, but usually will be permanentlyclosed. The operating end is adapted to be opened and closed, forexample, as is shown in FIGS. li through 5, wherein a shockandimpact-resistant swingable closure member, e.g., one or more doors,erected on the housing cylinder at the operating end of the module, isadapted to occupy an open or closed position with respect to the end ofthe housing cylinder in response to a force imparted by amotion-imparting means, e.g., an hydraulic cylinder, communicating withthe closure member from a location within the housing member. Theclosure member has an aperture or porthole therein which, when theclosure member is closed, falls on an axis which is coincident with theaxis on which the three working components of the module preferablysequentially coincide. The closure member is moved to the open positionwhen the drilling means, loader, or support means is to be moved axiallyto an extended position; and to the closed position when all axiallyextendable members are in the retracted position and the energy is to beemitted from the energyprojecting member. The porthole allows unimpededtravel of the energy from the energy-projecting member to the explosivecharge in the drill hole. A conical or wedge-shaped closureconfiguration is preferred as a means of providing added protectionagainst rock impacts. r

The effect of shock and impacton .the module can also be moderated byuse of energy-absorbing means together with the housing, e.g., by theuse of springs in the system for mounting the module on a supportingarm. A particularly useful energy-absorbing device is an inflatedpneumatic member, i.e., an elastic member holding fluid under pressure.Such a member, resembling an automobile tire in its function, forexample, when engaging the end of the housing cylinder, e.g., as shownin FIGS. 1 through 4, serves to cushion the front of the module from theimpact of shock waves and flyrock. Several such members can be employedside-byside around the housing when additional, and lateral, cushioningis desired.

In the process of this invention, greater efficiency is achieved, e.g.,in terms of weight of material excavated per unit time, by performingmultiple drill-load-blast sequences concurrently. With the module ofthis invention, multiple-sequence cycles are achieved by employing anumber of modules equal to the selected number of sequences to beperformed concurrently. Multiple modules each comprising a singledrilling means, single explosives delivery means, and singleenergy-projecting means, suitably supported and housed, can be employed.However, when efficient utilization of space and weight is of primeconsideration, it is preferred to employ a composite module whichincorporates two or more single-component modules or module unitssuitably clustered within a common housing member. The geometricarrangement or cluster pattern of the basic module units within thecomposite module, and the specific number of units, can vary asrequired. For example, for working concurrently in essentiallystraightline or block drill-hole patterns, a linear or block cluster ofunits can be employed, the overall configuration of the module in suchcases being essentially that of'a parallelipiped. For working in acurved pattern, the cluster may be in the form of an arc of a circle. Inthe composite module, each unit can be complete within itself, i.e.,have its own drilling means, explosives delivery means, andenergy-projecting means; or a common component, e.g., an explosivesdelivery means, can be shared by more than one unit.

Any type of drilling means can be used in the module, e.g., a percussiondrill or hammer, a rotary drill, or one employing both percussion androtary action. An electrical disintegration drill, providing heat androtation, also can be used. For hard rock, rotary percussion drills arepreferred. For convenience, i.e., in order to make use of ready-madecomponents, where available, and in order not to multiply the number ofconstructional ele ments unnecessarily, in a preferred module thedrilling means and support member constitute a rotary percussiondrilland feed, respectively, both constructed of metal, e.g., steel. Thedrill rotation can be imparted through a pneumatically or hydraulicallyoperated motor mounted in the feed channel, and axial thrust forextension and drilling can be applied through a heavyweight chain feeddriven by a pneumatic or hydraulic motor. The explosives delivery tubeand energyprojecting means are mounted on support'means, e.g., the drillfeed channel, in a mannersuch that axial motion of the drill and thedelivery tube is unimpeded.

The explosives delivery tube has an explosives feed end whichcommunicates with an explosives feed system located outside the confinesof the module. The explosives feed system is comprised of an explosivessupply unit, e.g., a magazine containing cartridged explosive or bulksolid explosive, or a storage and mixing tank for slurry explosiveingredients; and a feed unit associated therewith capable of deliveringthe explosive therefrom, e.g., a pneumatic loader for solid explosives,or a pump for slurry explosives. The tube from the module can beattached to the loading tube of a pneumatic loader or to the deliveryhose of a slurry pump; or, if long enough, it can replace the loadingtube or delivery hose entirely and be attached directly to theexplosive-delivery mechanism or pump in the explosives feed system. Forloading cartridged explosive, e.g., dynamites, a preferred feed unit isa pneumatic cartridge loader such as is described in US. Pat. No.3,040,615 and in The Modern Technique of Rock Blasting, N. Langefors andB. Kihlstrom, Stockholm, Almqvist & Wiksell, 1967, pp. 91-101. Thedelivery tube, both the portion thereof which is in the module and thatwhich is outside the module, should be somewhat flexible and can bemade, for example, of metal or plastic. With the pneumatic cartridgeloader, a semiautomatic breech piece can be used to feed cartridgescontinuously.

The axial motion of the tube with respect to the support can beaccomplished in any one of various ways. One way is to have a flexibletube, e.g., a plastic tube, lead into a rigid tube, e.g., a metal tube,which is slidably mounted on the support, e.g., in a guiding track, inthe desired position with its free end at the operating end of themodule and its other end in communication with a pneumatic positioningcylinder. In another method, i.e., that shown in FIG. 3, the tube may bemoved by means of a device, i.e., the so-called robot loader, which isalso described by N. Langefors and B. Kihlstrom, op cit. The robotloader acts in conjunction with a pneumatic cartridge loader. The robotloader, mounted on the support means, e.g., the drill feed channel,consists of a pneumatic cylinder which reciprocates a tubularpiston-rod. The delivery tube is inserted axially through the pistonrod. To the piston-rod is connected a pneumatic grip arrangement, a handwhich holds the tube by friction so that it undergoes reciprocatingmotion. As the tubular piston-rod reciprocates, the pneumatic hand gripson forward movement and releases on backward movement, thus imparting anincremental forward motion to the delivery tube. For retracting the tubeafter the drill hole has been loaded, the reverse hand action takesplace. Preferably, the delivery tube is passed down to the bottom of thedrill hole and moved out slowly with repeated light countermovements soas to pack the ejected cartridges to high density.

In a preferred module, the energy-projecting means is a gun. The termgun denotes an assembly which includes a metal tube or barrel having oneopen end (the muzzle end) and the other end (the after end) adapted toform a chamber into which projectiles are introduced and gas underpressure is admitted or generated rearward of the projectiles uponcommand. The

term is meant to include devices in which projectiles are propelled bygas admitted into the chamber at high pressure, as well as those inwhich the propellant gas is produced in the chamber by the burning of apropellent composition. When required, as in the latter case, the

after end of the barrel is closed off by a breechblock or plug, seatedin a housing which can be opened, for loading ammunition into thechamber (forward of the plug), and closed, for igniting the propellentcharge, by a breech mechanism upon command. The type of gun employed isnot critical provided it is capable of propelling projectile material ofsufflcient mass at sufficiently high velocity to subject the explosivein the drill hole to high enough pressure over a sufficient area andtime that the explosive is caused to detonate. The impact energyrequired is more readily attained with solid projectiles, andparticularly unitary solids, i.e., bullets as contrasted with shot, andfor this reason bullets are the preferred projectiles. Also, while theprojectile can be propelled by a stream of gas admitted into the chamberat high pressure, as in an air gun, there is less restriction on theattainable impact velocity when the projectile is propelled by theburning of a propellant composition in the chamber. Consequently, gunswhich operate on the propellant burning principle are preferred. Thus,in the preferred embodiment the gun consists of a metal barrel havingits after end closed off by a breechblock or plug which can be opened,for loading an ammunition round into a chamber forward of the plug, andclosed, for igniting the propellant charge in the round, by a breechmechanism operating upon command from outside the module. Emptycartridge cases can be continuously ejected from the module, orcollected in a container provided for the purpose in the module, thecontainer being adapted to be emptied periodically. The ammunitionprimer can be a percussion primer, electric primer, or a combinationprimer. Electric firing of the primer may be preferred in certain caseswhen greater precision with respect to time intervals betweendetonations is required.

The magazine for the ammunition can be located inside or outside theconfines of the module. An external magazine is preferred because ofspace restrictions in the module and also because storage of ammunitionat a location removed from the operating area is desirable from a safetyviewpoint. Therefore with external storage, a loading or delivery tubefor ammunition leads from an external ammunition feed system to thechamber of the gun. The feed system can be, for example, a pneumaticloader such as has been described for loading cartridged explosive intoa drill hole.

While the gun may be constructed completely according to custom design,in most cases it will be possible to adapt a commercially available gun,e.g., a boltaction rifle, semi-automatic rifle, or pistol, for use inthe module. Rifling of the bore, while desirable, is not strictlyrequired owing to the relatively small distances over which theprojectile will travel when the module is in operation. Remote firing ofthe gun can be accomplished by applying electrical current to a solenoidwhich actuates a conventional mechanical firing linkage, i.e., triggeraction to cause motion of the firing pin to ignite the ignition mixtureby percussion; or by applying current to an insulated firing pin incontact with a bridge wire or an electrically-conductive ignitionmixture in an electric primer, the electrical circuit being completedthrough the cartridge case and ground, and the ignition mixture beingignited by ohmic heating of the bridge wire or conductive mix.

When a laser is used as the energy-projecting means, a housing member isrequired to prevent the entrance of light-absorbing material, such asrock dust, into the path of the laser beam. The laser includes a laserrod (e.g., ruby), a total reflector at one end, and a partial reflectorat the other. end of the rod; one or more flash lamps to pump the laserrod; a high-voltage electrical power source to excite the flash lamp(s);a Q-switch or Q-spoiler in the path of the beam between the front end ofthe rod and the partial reflector; and a focussing lens. To affordmaximum protection to the laser during the blast, it is preferred thatthe laser be in an offset position with respect to the beam path. Forexample, the laser can be mounted in the wall of the housing and thebeam reflected onto the desired path by suitably positioned reflectors.In such a case, if positioning of the functioning components onto acommon axis is employed, the reflectors can be positioned on a supportmeans and moved thereon to project the beam on the required path.

The module also contains, or is in communication with, suitablemotion-imparting mechanisms, e.g., hydraulic or pneumatic devices, whichperform such movements as axially moving the drilling means, explosivesdelivery tube, and support means (e.g., drill feed channel); drilling;delivering explosives to the drill hole; in a preferred embodiment,delivering ammunition rounds to the gun chamber and tiring the gun;repositioning the basic components (i.e., indexing) and opening andclosing the housing door at the operating end. Such mechanisms arewell-known to those skilled in the art and their basic mode of operationtherefore will not be described herein. All power supply lines, e.g.,hydraulic lines, for such devices are shielded in the same way as arethe module components, preferably by surrounding them in a suitablehousing member. When the module includes a housing member, the powersupply lines pass into the module through the housing wall via themounting member, or via one or more special apertures provided therefor.

As stated previously, the module of the invention, when positioned neara surface of material to be worked, e.g., a rock face, and suitablyenergized, can in rapid sequence drill a hole in the rock, loadexplosive into the hole, and initiate the explosive by the rapid releaseof energy therein, e.g., projectile impact. Inasmuch as the operation ofthe module produces an explosion each time the energy enters theexplosive, the module must be mechanically mounted on a supporting armor base and its functioning controlled from a suitably shieldedlocation. While any mounting and control scheme can be employed, e.g.,impactand shockresistant jack leg or jack bar mounting with powercontrols separated from the mass being worked by a barricadesubstantially parallel to the mass, the fullest benefit of the module isderived when it is incorporated into a machine adapted to support,maneuver, and operate one or more of the modules in a substantiallycontinuous manner. For this reason, the module(s) usually will bemounted on a vehicle, such as a truck, and manipulated by personnel froma location inside the vehicle, the vehicle and personnel being suitablyprotected from the effects of the relatively small blasts.

For a clearer understanding of the process and module of this invention,reference is now made to the drawing, which illustrates the structureand mode of operation of typical modules, and a typical cyclic patternin which the process can be carried out.

In FIGS. 1 through 4 a module is in position before rock face 1 on alongitudinal axis which is substantially normal to face 1 and parallelto face 2. Each basic working component of the module is shown in threedifferent radial positions, the drilling means being in the vertialplane of view in FIGS. 1 and 2, the explosives delivery tube in FIG. 3,and the energy-projecting means in FIG. 4. When a working component isin this vertical plane, the longitudinal axis of the componentsubstantially coincides with the axis of the drill hole (indicated by adotted line into the rock in FIG. 1).

Referring to FIGS. 1, 1A, and 2, elongated support means 3, e.g., adrill feed channel, has drilling means mounted thereon, shown as arotary percussion drill, having an elongated tubular member 4, e.g., adrill steel, and bit 5. The drilling means is movable axially on supportmeans 3, e.g., through a chain feed or screw feed driven by a motor 6,for example an air motor. The motor-driven chain feed or screw feedapplies feed pressure or thrust for drilling. Drill action(reciprocation and rotation) is provided by a motor 7, e.g., apneumatically operated motor. Support means 3 communicates with amechanism 9, e.g., an hydraulic cylinder, which is adapted to movesupport means 3 back and forth independently in an axial direction in anaxial groove in slide member 37 (3 shown extended in FIG. 2).Groove-containing slide member 37, attached pivot member 8, having anaxis of rotation parallel to the axis of elongated member 4, and flange12 together constitute the mounting member for the module. An indexingmeans 31, in this case an hydraulic cylinder (shown in FIG. 1A),communicates with slide member 37 and housing 13, e.g., a metalcylinder. A pointed metal peg or stinger extends axially from the end ofsupport means 3 which faces face 1, and hook-like guide elements 1 Iextend from support means 3 at the same end, normal to the longitudinalaxis, in a manner such that elongated member 4 passes through guideelements 1 1. Flange 12 attached to pivot member 8 fits through anaperture in the wall of housing 13, flange 12 being adapted to engage amounting member 14 of a suitable supporting arm for the module. At theoperating end of the module, i.e., where drill bit 5 is located, aninflated pneumatic member 15, e.g., a rubber tire, engages the end ofhousing 13. At this same end, a closure member 16, e.g., a door, isadapted to open or close by actuation of a motor 17, e.g., an hydraulicmotor, mounted inside the housing and communicating with closure member16. The latter has an aperture or porthole 18 therein, so positionedthat when the closure member is closed the axis on which the'workingcomponents sequentially coincide (elongated member 4 axis in FIG. 1)passes through aperture 18.

In FIG. 3, 19 is an explosives delivery tube, somewhat flexible, e.g.,made of plastic, and mounted on support means 3 substantially parallelto elongated member 4, and at the same radial distance as the elongatedmember from the pivot member 8. One end of tube 19 leads to aconventional explosives feed system, e.g., a pneumatic cartridge loader,as described previously, located outside the confines of the module. Theother, free end of the tube is the discharge end and is located at theoperating end of the module. Tube 19 passes through the aperture in thewall of housing 13. 20 is a feed mechanism adapted to move tube 19axially, e.g., a robot loader such as has been described above.Ring-like guide elements 21 extend from support member 3 at theoperating end normal to the longitudinal axis, in a manner such thattube 19 passes through the guide elements.

In FIG. 4, 22, 23, and 30 are the barrel, chamber and breech housing,respectively, of a rifle, and 24 is a flexible ammunition delivery tubewhich leads into the gun chamber 23 and communicates with an ammunitionfeed system, e.g., a pneumatic loader as previously described, locatedoutside the confines of the module, tube 24 passing through the aperturein the wall of housing 13. The rifle is fixedly mounted on support means3 substantially parallel to elongated member 4 and at the same radialdistance as the elongated member and explosives delivery tube from pivotmember 8. The gun muzzle is at the operating end of the module.

Prior to a drill-load-blast sequence, the module is positioned as shownin FIGS. 1 and 1A, elongated member 4 being coaxial with the axis of thedrill hole desired, and in a vertical line with pivot member 8. Motor 17has been energized to allow closure member 16 to open. In the first stepof the sequence (FIGS. 2 and 2A), energizing of mechanism 9 movessupport means 3 on slide member 37 axially in the direction of face 1until stinger 10 firmly engages face 1, helping to stabilize the modulewhen the components are extended. With the support means in thisposition, the elongated member 4 is moved axially in the direction offace 1 by energizing of motor 6, the drill bit then boring a hole 25 ofthe desired depth in the rock by the thrust and rotating action impartedto it by the chain or screw feed and motor 7.

After the hole has been drilled, the chain or screw feed acts to retractthe drilling means back into the housing 13, and hydraulic cylinder 31moves slide member 37 so that support means 3 mounted thereon rotates ina counter-clockwise direction by the action of pivot member 8 so as toposition explosives delivery tube 19 coaxially with hole 25 and on avertical line with pivot member 8 (FIGS. 3 and 3A). Tube 19 movesaxially and into drill hole 25 by the action of feed mechanism 20. Whilethe delivery tube is in this position, cartridges of condensed highexplosive 26 are fed through tube 19 and ejected therefrom into hole 25,e.g., by means of a pneumatic cartridge loader.

After the hole has been loaded with explosive, feed mechanism 20 acts toretract tube 19 back into the housing 13, and hydraulic cylinder 31again is operated, this time moving slide member 37 and support means 3mounted thereon, in a clockwise direction so that rifle barrel 22 iscoaxial with hole 25 and on a vertical line with pivot member 8 (FIGS. 4and 4A). Closure member 16 is closed by energizing motor 17, aperture18, which is larger in diameter than the bullet 27 employed, beingcoaxial with hole 25. The rifle is fired, e.g., by applying current tothe firing pin of the ammunition primer, propelling bullet 27 at highvelocity from the rifle muzzle, through aperture 18 and the spacebetween the module and hole 25 and into explosive 26 in the hole 25,along the trajectory indicated by the dotted line. The impact causes theexplosive to detonate, and the rock to break and move in a manner astypified in FIG. 4.

FIG. 5 shows a portion of a module similar to that shown in FIGS. ll-4,with the exception that in this embodiment a laser is theenergy-projecting means, and the design of closure member 16 ismodified. The module is shown with components operating in the intiationstep of the sequence. In FIG. 5, a laser assembly 32,

i.e., rod, lamps, Q-switching device, partial and total reflectors, andfocussing lens, is mounted on the wall of housing 13. Laser assembly 32is connected to a power supply located outside the confines of themodule. The laser assembly is located off the drill hole axis. The laserbeam 33, after passage through the focussing lens in laser assembly 32,is reflected from parallel reflectors 34 and 35 which direct the beamonto a path coaxial with the drill hole 25. Explosive 26 in the drillhole has a transparent end-cap 36, e.g., a cartridge end, made, forexample, of plastic. The module is in a position relative to face 1 suchthat the focaTpoint of beam 33 is on the surface of explosive 26.Reflectors 34 and 35 are mounted on support member 3 in a manner suchthat operation of indexing means 31 causes the reflectors to adopt aposition such that the path of the beam 33 is coaxial with hole 25.Closure member 16 is wedge-shaped, and has upper and lower portionswhich are adapted to open and close. Energizing of the power supply tolaser assembly 32 causes emission of a beam 33 of electromagneticradiation, which travels through the atmosphere to hole 25, passesthrough transparent end-cap 36, and focusses on the surface of charge26, causing the charge to detonate.

Typical ways in which the present process and module can be operated towork a geological mass are described in the following examples.

EXAMPLE 1 As illustrated in FIG. 6, a face 1, substantially flat andvertical, has been opened up in a geological formation such as hardrock, and the face is being advanced, e.g., to drive a tunnel, by theprocess of this invention. The face is substantially square and is 8feet high and 8 feet wide. Each round (all of the sequences or holesneeded to advance the entire face) consists of 30 holes arranged inparallel columns and rows spaced, for the most part, equidistant fromeach other. That is, the drill-load-blast sequence of the presentprocess is carried out at 30 locations. The process is being effected insuccessive groups of sequences, or five drill-loadblast cycles pertunnelling round, with six sequences, or holes, per cycle. Six modulesare employed. In each cycle, six holes are drilled substantiallysimultaneously and then loaded substantially simultaneously, and thensix bullets are propelled, one into each loaded hole, withinmilliseconds of each other so as to detonate the six charges, the cyclebeing ended when the continuity of the series of detonations isinterrupted for the time interval required to drill a new series ofholes (the beginning of the next cycle).

In the situation shown in FIG. 6, the first three cycles (three centerrows, designated Cycles 1, 2, and 3) have been concluded, and the fourthcycle, 4, is in progress at the blast step of the sequence. The blastingwhich has been completed has produced rock fragments which haveseparated from the mass forming horizontal faces 2a and 2b substantiallythe depth of the drill holes and in planes substantially those of theoriginal holes of The holes are 1.25 inch in diameter and 1.5 feet long.Each hole is filled, and contains approximately one-half pound ofcartridged GELEX 2, a semi-gelatin dynamite. (See Examples 2-6). Thedrills on the modules are rotary percussion drills, and the loaders arepneumatic cartridge loaders in which the dynamite cartridges are pushedforward through loading tubes and ejected into the drill holes, whilethe cartridge paper is slit and the explosive is packed to high density.The guns are rifles employing commercial 0.22-caliber ammunition rounds,and they are fired on an axis with the holes from a distance of 10 feet,providing an impact velocity of 3,000 feet per second. Each cycle iscompleted in about 2.5 minutes, the total dead time within the cyclebeing about 45 seconds. In FIG. 6, the six holes in Cycle 4 have beendrilled and loaded with explosive 26. The bullets 27 are shown justbefore impact. Impact of the bullets with the charges (at about 2millisecond intervals) causes detonation and rock breakage with theformation of new face 29 to the level of the holes in Cycle 4.

The procedure described for Cycle 4 is repeated for Cycle 5 afterclearing any pieces of rock obstructing the drill hole positions (at thelocations marked with to expose the complete new face.

The following examples serve to illustrate the performance of theprocess of this invention using a highvelocity bullet as the propagativeenergy for initiating the explosive, the process being illustrated withdifferent combinations of conditions, i.e., explosive composition, drillhole conditionspand bullet impact velocity, mass, and trajectory. Theimpact velocities exemplified should not be interpreted as being limitvelocities for the systems shown, and in any event the operating limitscould be changed as conditions such as have been described were changed,e.g., confinement, contact area, or explosive density. Unless specifiedotherwise, in each example in the first step of the sequences a1.75-inch-diameter 12-inch-long hole is drilled in a rock mass. The holethen is loaded with condensed high explosive, and the explosive isinitiated by firing a bullet from a rifle, which is aligned coaxiallywith the hole except where specified otherwise. The rifle is triggeredremotely. The distance between the riflemuzzle and the hole is about 10feet. The impact velocity given is the velocity of the bullet obtainedwith the ammunition used and measured 15 feet from the muzzle. Exceptwhere noted otherwise, the bullets used are soft-point (unjacketed tip)bullets. Where material other than explosive is present in the drillhole, the bullet passes through the other material, impacting theexplosive last. In each example, the drill-load-blast sequence isfollowed by a second sequence at a different location from the first,and effected under the same conditions as the first. In every case, theexplosive charge detonates, fracturing the rock.

Elxam Secondary Explosive Ammunition (Bullet Wt.) Drill Hole ConditionImpact Velocity (ft/sec) p e i 2" Gelex" 2 .22'caliber (3.54 g.)Explosive only 3600 3 Gelex 2 .22-caliber (3.54 g.) Explosive only 28004 Gelex" 2 .30-caliber (9.57 g.) Explosive only 2800 5 Gelex" 2.22-caliber (3.54 g.) Explosive only 1500 6 Gelex 2 .22-caliber (3.54g.) Explosive in paper cartridge 2800 (fully jacketed) (%-in.-thickend), covered by 4 in. of water 7 Hi-Cap .22-caliber (3.54 g.) Explosiveonly 3600 8 Hi-Cap .22-caliber (3.54 g.) Explosive only 2800 9 Hi-Cap.30-caliber (9.57 g.) Explosive only 2800 10 Hi-Cap .22-caliber (3.54g.) Explosive covered by 4 paper 2000 cartridge ends (L5 in. totalthickness) 1] Hi-Cap" .ZZ-caliher (3.54 g.) Explosive plus l2in. aircolumn 2000 12 Hi-Cap" .22-caliber (3.54 g.) Explosive only 2000 (l5 offdrill hole axis) 13 Hi-Cap .22-caliber (3.54 g.) Explosive only 800 10off drill hole axis) 14 Water-Gel Explosive .22-caliber (3.54 g.)Explosive only 3600 I5 Water-Gel Explosive .22-caliber (3.54 g.)Explosive only 2800 16 Water-Gel Explosive .30-caliber (9.57 g.)Explosive only 2800 Semi-gelatin dynamitc (63% ammonium nitrate. 2071nitroglycerin) Ammonia dynamite (51% ammonium nitrate, 87:nitroglycerin) 32% Ammonium nitrate, 15% sodium nitrate 45% of an 8671uq. soln of monomcthylaminc nitrate. 3V1 ferrophosphorus 371 line flakeAl powder. and 4% H O.

"" l-in.-diam., 8-in.-long hole EXAMPLE 17 The present process isemployed to accomplish secondary blasting, i.e., to break up large rocksproduced from a previous blasting operation. A single module of the typeshown in FIG. 5 is employed, the module being 35 mounted on, andoperated from, a vehicle, which moves along the surface among the rocksas required to perform a required succession of drill-load-blastsequences. The drill and loader, and the hole and charge size, are thesame as in Example 1, except that in this case the bottom (outside end)of the outermost cartridge consists of a 0.5-inch thick disk oftransparent plastic, e.g., polystyrene. The energy-projecting device inthe module is a laser. head, model LHM6, manufactured by RaytheonCompany, the laser head comprising a ruby rod 6 inches long and /8 inchin diameter, two FX-47A-6.5 flash lamps, a front mirror which is 65%reflective at 6,950A, and a 99.9% reflective rear mirror. Q-switching isachieved by placing a cell filled with a passive liquid Q-switchsolution in the path of 50 the beam between the front end of the rod andthe 65 mirror. A focussing lens (focal length 45 inches) is positionedforward of the 65% mirror. The laser head, Q- switch solution, and lensare mounted to the wall of the housing. Two total reflectors(right-angle glass prisms) are positioned forward of the lens in amanner such that the axis of the focussed beam is shifted from that ofthe laser rod to an axis parallel thereto, but separated therefrom by 6inches. The reflecting prisms are mounted on the drill feed channel.During operation,

the module is positioned so that the laser beam is aligned coaxiallywith the drill hole, and the distance between the charge in the drillhole and the prism nearest to it is 36 inches. After the hole has beendrilled and loaded, the laser is activated by application of ahighcurrent pulse to the laser head from a remote power supply unit(Raytheon Model LPS4, with LPS4A control chassis and LPS4B capacitorbanks) having a 2,200

1. A process for advancing an underground rock face which comprisesperforming a plurality of substantially continuous drill-load-blastsequences substantially concurrently as a group at different locationsin the rock, followed by other such groups of sequences in a manner suchas to produce a substantially continuous suc- 40 cession of groups ofsequences, the number of said sequences carried out substantiallyconcurrently as a group being less than about 35% of the total number ofsequences in said succession, each substantially concurrent group ofsequences producing a portion of a new face and said succession ofgroups producing an entire new face, each of said sequences comprisingthe steps of (a) drilling a hole in the rock from the face to beadvanced, (b) placing a charge of condensed, exclusively secondaryexplosive in the hole, and (c) initiating the explosive charge in thehole by causing energy to be released into the charge by the impact of aprojectile with the charge, by the impingement of a focussed laser beamonto the charge, or by the discharge of a spark from an electrode to thecharge, said energy being pro- 5 jected to the charge from a locationwhich is separated from the hole by a distance of less than about 30feet and being released into the charge at a rate sufficiently high tocause detonation thereof, and a separate pulse.

of energy being released for the initiation of each charge.

quences in said group before Step (0) is begun in any of said sequences.

3. A process of claim 1 wherein said condensed secondary explosive isdynamite.

projectile upon impact is at least about 1,500 feet per second.

8. A process of claim 1 wherein the energy is released into the chargeby impingement of the focussed output of a laser on said charge.

9. A process of claim 1 wherein the compressive strength of the rock isat least about 15,000 psi.

1. A process for advancing an underground rock face which comprisesperforming a plurality of substantially continuous drill-load-blastsequences substantially concurrently as a group at different locationsin the rock, followed by other such groups of sequences in a manner suchas to produce a substantially continuous succession of groups ofsequences, the number of said sequences carried out substantiallyconcurrently as a group being less thaN about 35% of the total number ofsequences in said succession, each substantially concurrent group ofsequences producing a portion of a new face and said succession ofgroups producing an entire new face, each of said sequences comprisingthe steps of (a) drilling a hole in the rock from the face to beadvanced, (b) placing a charge of condensed, exclusively secondaryexplosive in the hole, and (c) initiating the explosive charge in thehole by causing energy to be released into the charge by the impact of aprojectile with the charge, by the impingement of a focussed laser beamonto the charge, or by the discharge of a spark from an electrode to thecharge, said energy being projected to the charge from a location whichis separated from the hole by a distance of less than about 30 feet andbeing released into the charge at a rate sufficiently high to causedetonation thereof, and a separate pulse of energy being released forthe initiation of each charge.
 2. A process of claim 1 wherein saidplurality of sequences in a group are synchronized in a manner such thatSteps (a) and (b) are completed in all of the sequences in said groupbefore Step (c) is begun in any of said sequences.
 3. A process of claim1 wherein said condensed secondary explosive is dynamite.
 4. A processof claim 1 wherein said condensed secondary explosive is a water-bearingexplosive.
 5. A process of claim 1 wherein said energy is released intothe charge by the impact of a projectile therewith.
 6. A process ofclaim 5 wherein said projectile is inert.
 7. A process of claim 5wherein the velocity of said projectile upon impact is at least about1,500 feet per second.
 8. A process of claim 1 wherein the energy isreleased into the charge by impingement of the focussed output of alaser on said charge.
 9. A process of claim 1 wherein the compressivestrength of the rock is at least about 15,000 psi.